1. Field of the Invention
This invention relates generally to a laser ablation system and in particular to a laser ablation nozzle assembly.
2. Description of the Related Art
Laser ablation and in particular ultraviolet (xe2x80x9cUVxe2x80x9d) laser ablation is widely used, for example, to remove materials from substrates. Such materials may be inorganic or organic (e.g., photo-resists and polymers) and often these to-be removed materials are in thin-film form coated on a substrate. For example, materials are removed using laser ablation to produce a via hole so that there is electrical contact between a top conductive layer and a bottom conductive layer through the via hole. In another example, materials are removed from areas of a thin-film electronic device using laser ablation so that those areas can be used to encapsulate the electronic device. In this case, an inorganic substrate (e.g., a glass substrate) is coated with organic layers (e.g., photo-resist layers or polymer layers) and the resulting electronic device is encapsulated by mating a cover/encapsulating sheet (e.g., metal cans and glass sheets) with the substrate by gluing the two together with, for example, a UV-cure material. Often, however, the bonding of the glue to the substrate when certain organic layers are present on the substrate is not good and hence laser ablation is used to remove the organic layers from the substrate to allow for better bonding between the cover/encapsulating sheet and the substrate.
In yet another example, laser ablation is used where an inorganic substrate (e.g. a glass substrate) is coated with organic layers (e.g., photo-resist layers or polymer layers) and the resulting electronic device is encapsulated with a sputtered or evaporated organic and/or inorganic material. Bonding between the encapsulating material and the substrate when the organic layers are present on the substrate is not good and hence laser ablation is used to remove the organic layers from the substrate to allow for better bonding between the encapsulating material and the substrate. Materials may also be removed from areas on the electronic device which when exposed to humidity and oxygen cause corrosion.
Laser ablation systems that perform the above functions are commercially available from, for example, Resonetics Corporation of Nashua, N.H., or Exitech Limited of Oxford, England.
FIG. 1 shows a prior art laser ablation system 103. The laser ablation system 103 includes a nozzle assembly 134 that includes a nozzle 113 and a window 122. The nozzle 113 has a top end and a bottom end. The window 122 is on the top end of the nozzle 113 and the bottom end of the nozzle is in close proximity to a target 110 (e.g., a substrate) on which the materials (e.g., polymers, photo-resists, and thin films) that are to be laser ablated reside. A laser beam 125 enters the nozzle 113 by passing through a window 122 that is transparent. The window 122 may be comprised of transparent materials such as, for example, quartz or glass. The laser beam 125 is generated by a laser assembly 131 located above the nozzle 113. The laser assembly 131 includes the laser, laser optics, and other components used to generate and position the laser beam 125. The window 122 protects the laser optics and other components within the laser assembly 131 from debris 116. The laser beam 125 travels from a top end of the nozzle 113 to the bottom end of the nozzle 113.
The debris 116 is generated by the laser beam 125 ablating the materials resulting in ejection of the debris 116 from the ablation point. Suction pumps can be used to create a vacuum or a gas flow within a vacuum channel 119 to remove the debris 116 by sucking the debris 116 away from the target 110. However, even with the vacuum or gas flow, the debris 116 may be re-deposited on the target 110 around the ablation point, and/or the debris 116 may be re-deposited on the window 122 thus obstructing the laser beam path. When the debris 116 is re-deposited on the target 110, the re-deposited debris can cause, for example, weaker bonding between the target 10 and the glue, or contaminate the target 110 thus adversely affecting the electrical/optical performance of the resulting electronic device fabricated on the target 110. When the debris 116 is re-deposited on the window 122, the debris 116 can cause a reduction in the laser beam intensity at the ablation point, fluctuation in beam intensity at the ablation point resulting in poor uniformity in processing the materials, rapid degradation of the window, permanent window damage, and high costs associated with frequent replacing or cleaning of the window.
Therefore, there is a need to reduce the debris deposition on the window and also to reduce the amount of debris being re-deposited onto the target.
An embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces debris deposition on a window. The embodiment of the nozzle assembly includes a nozzle that has a top end and the window is located on the top end of the nozzle. The window has at least one aperture and a laser beam is emitted through a particular one of the at least one aperture.
An embodiment of a method is described that, for example, reduces debris deposition at one or more points on a window of a laser ablation system. The embodiment of this method includes generating a laser beam, and emitting the laser beam through an aperture at one of the points on the window.
Another embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces debris deposition on the window. This embodiment of the nozzle assembly includes a nozzle having at least one channel at a top end of the nozzle, a window located on the at least one channel, and a gas that flows through the at least one channel. The gas flow through the at least one channel reduces debris deposition on the window.
Another embodiment of a method is described that, for example, reduces debris deposition on a window of a laser ablation system. This embodiment of the method includes moving a gas through at least one channel that contacts the window to reduce the accumulation of debris on the window.
Yet another embodiment of a nozzle assembly within a laser ablation system is described that, for example, reduces the debris being re-deposited onto a target. This embodiment of the nozzle assembly includes a nozzle that has a central channel aligned longitudinally and through which a laser beam travels from a top end of the nozzle to a bottom end of the nozzle. The nozzle assembly also includes a window located on the top end of the nozzle. In this embodiment, the central channel is threaded.